the thought of covering the entire car body with a layer of veil seems exceptionally daunting....
I'm not convinced it's essential to cover the whole surface, I have never done that on either car and generally speaking the only cracks that reappear have done so due to impact or a poor repair on my part. For example on my Europa there are a couple of hairline cracks immediately in front of the front bonnet and that's almost certainly down to the careful way I slipped and dropped the lid during re-assembly in 2011. Otherwise they don't usually come back if repaired properly with surface tissue/resin - in fact the ones I referred to are "new to me" because I've never seen crazing in that location before !
But if you're a professional then the one way to be certain not to get an angry customer is to resurface the entire car. It's the nuclear option and the customer pays for the time but is rewarded with a concours finish.
My take has been to only resurface areas where I've seen problems or done repairs. If you strip back to gelcoat and don't see any crazing on the bare fibreglass (wet wipe with thinners or similar to highlight defects) then I don't see any point in stripping off one good surface simply to replace it with another.
The Europa was done in 2011 and the only area of crazing is the 2/3 lines previously mentioned. The Elan was done in 2013 and had a lot more work with the doors being remodelled to fit (an S3 "feature") and deep repairs on the front wings, rear deck & boot lid, mainly due to helpful people leaning on the rear boot lid when it was open. No, I don't understand why they did it either, but they won't do it again...... anyway, 8yrs and 6yrs on, they both still look pretty fair.